Sized paper



Patented Aug. 17, 1937 UNITED STATES PATENT OFFICE SIZED PAPER tion of Delaware No Drawing. Application July 9, 1934, Serial No. 734,432

Claims.

This invention relates to an improved sized paper particularly of the type commonly designated book paper.

I have found that by both engine or furnish 5 sizing and surface sizing a paper stock containing a substantial amount of a finely divided filler composed largely of a calcium salt, such as calcium sulfite or calcium phosphate, which will not react detrimentally with the sizing substances, 2.

greatly improved paper sheet will be produced. Such a sheet, when calendered, can be scarcely distinguished from a coated paper and may be substituted for coated paper in most, if not all, of the uses of the latter. It may be provided with an extremely smooth, white, glossy finish and has a, very desirable ink receptivity.

The fibrous paper stock employed in the production of the improved paper may be of any of the types suitable for book papers. It may, for

example, be entirely composed of a sulfite pulp or-a soda pulp although I prefer to employ a mixture of these pulps. Other types of pulp might also be used. To this should be added sufiicient filler of the character mentioned, preferably calcium sulfite, to provide an ash content, in the final sheet, of between 10 and 40%, preferably between 20 and The calcium sulfiite for this purpose should be in an exceedingly fine state of subdivision and may conveniently be pro- 30 duced by precipitation from milk of lime or a suspension of finely ground calcium carbonate through the action of sulfur dioxide, in the manner set forth in my Patent No. 1,984,188 granted December 11, 1934. It may be used alone or in conjunction with other fillers not adversely affected by the usual sizing ingredients. All or part of the calcium sulfite might, for example, be replaced by a fine precipitated calcium phosphate. A portion of it might be replaced by a finely ground china clay but in that event the clay should not form more than 50 per cent of the filler. If too much clay is used the resulting product will be inferior. In fact for best results a filler that is substantially 100% calcium sulfite should be used.

The filler may be introduced at any convenient point in the system. Most conveniently it may be added to the furnish in the beater so that it may be thoroughly incorporated in the fibrous mass. It may, however, be added at a subsequent point up to the point where the paper leaves the paper machine wire in its transfer to the first press. Thus it may be added in the beater chest or in the Jordans or in the Jordan chest, or at the head box, or the rifliers. or the white water recirculating pump, or under the wire of a table roll or wire guide roll. It is preferably added as a suspension in water and for best results calcium sulfite or calcium phosphate should be added while in its original suspension 5 as freshly precipitated. i

In order to improve the character of the finished product and to give the stock suflicient wet strength to enable it to be treated in the desired manner a suitable size should be added to the 10 stock, preferably at the beater. -For this purpose rosin, wax, rosin-wax, emulsified oils, or salts of fatty acids such as stearates, may advantageously be employed. While it is considered best to precipitate the size in the beater by the action of 15 alum, with or without the assistance of ah acid, it may, if desired, be added in other ways and at a later stage as at the white water recirculating pump, or the head box of the paper machine, or at the guide roll. If desired the sizemight be 20 added jointly with the filler and for this purpose might be co-precipitated with the filler. For example, by co-precipitation a calcium sulfite filler might be sized by stearate, emulsified oils, waxes, or the like, and the sized filler then added to the 25 fibrous stock at any convenient point. The quantity of size employed may be varied to suit particular circumstances, depending upon the quantity of filler used and the character of the final product desired. Ordinarily between 1 and 3% 30 of the weight of the dry fibre will be satisfactory.

A small amount of starch may advantageously also be added to the furnish as a part of the size or with the filler. For example 30 to 40 pounds of starch may be added for each 1000pounds of 35 calcium sulfite.

To insurethe proper setting of the rosin size the furnish containing the fibers, filler, and size should be maintained on the acid side, i. e. witha pH below 7.0 and preferably between 5.5 and 40 6.5, by the use of sufficient alum or other acidic substances.

Thepaper stock containing the filler and size in the manner set forth is formed into a. continuous sheet on a paper machine and is then 45 surface sized in some convenient way. For this purpose I preferably employ a mixture of starch and glue in the proportion of about 8 to 10 parts of starch for 1 part of glue. Other substances might be substituted in whole or in part for 5 either of these ingredients. For example, a pentosan produced from straw might be used in place of starch and casein might .be used with or in place of glue. Various resin suspensions might also be employed. The surface size is 55 ,fied hydrocarbons such as. paraflin wax or preferably applied by means of a size press, the solution employed containing, for best results.

about 0.3 pound of starch per gallon with or without glue. Paper weighing say, 45 lbs. per ream should ordinarily have about 0.25 lb. of the surface size per ream. Both surfaces of the sheetmay be sized in this}. manner, if desired. In lieu of employing a size press the sizing solution may, if preferred, besprayedonto one or both surfaces of the sheet or it may be applied at the calender roll. v

For purposes of illustration several typical examples of mixtures and modes of procedure which have been found to produce particularly good results will. now be explained.

Example 1. A fiber'furnish consisting of about 50% sulfite pulp produced from coniferous wood and 50% soda pulp produced from deciduous wood is introduced into the beater of suitable papermaking equipment. Sufilcient calcium sulfite is added to the beater to provide an ash content between 27 and 28%. Rosin-wax is also added to the beater in an amount constituting approximately 2% of the weight of the dry fiber. Alum to theextent of about double the weight of the rosin-wax should also be added to precipitate the rosin-wax and insure a pH value 'of the furnish below 6.8. The furnish isnow passed through the usual equipment and is thoroughly jordaned on its way to the paper machine. A, continuous sheet is produced on the paper ma.- chine with suflicient strength to withstand the surface sizing operation which is later performed by a size press. vThe thickness of the webmay suitably be such as to produce a final product having a basis weight of about 57 lbs., 1. e. for

500 sheets 25 x 38". The size press applies to one or both surfaces of the sheet, a sizing solution containing 0.3 lb. of starch per gallon and one part of glue for each ten parts of starch. The surface-sized sheet is then calendered.

Example 2.The beater is furnished .with 800 lbs. of sulfite pulp, 1000 lbs. of soda pulp, 200 lbs. of old paper stock, 20 lbs. of rosin size, and 40 lbs.

of alum. To this furnish'is added a suspension of calcium sulfite containing about .5 lb. of the sulfite per gallon and containing 30 lbs. of starch for each 1000 lbs. of the sulfite. Sufllcient calcium sulfite is added to provide an ash content of 30%. in the final product. This stock is formed into a continuous web on a paper machine and is surface sized by spraying onto one or both surfaces a solution containing .25 lb. of starch per gallon with .03 lb. of glue. The resulting sheet is super calendered. To assist in overcoming the two-sidedness of the paper a portion or all of the calcium sulfite suspension may be applied at the'guide roll, under the wire. For each 1000 lbs. of calcium sulfite there may also be added, if desired, about 8 lbs. of emul'si fatty acids or. lubricating oil; Example 3.The beater maybe furnishedswith 800 lbs. of sulfite pulp, 300 lbs. of soda pine and 900 lbs. of soda pulp with 20 lbs. of Bennett No. 18 size (an emulsified rosin, paraflln and Montan wax mixture) and 30 lbs. of alum. The pulp is moderately beaten and the pH adjusted to around 5.5 to 5.0 by the addition of alum. A

suspension-oi calcium sulfite is prepared con- 4 Brightness scope inlet of the white water pump in such quantity as to provide an ash content of between 28 and 31%. A uniform sheet is produced from this stock and this is then surface sized in a size press I with a solution containing 30 lbs. of starch and 5 lbs. of glue for each gallons. The sheet is then given two passes through a super-calender.

Papers produced in accordance with the foregoing are superior to any sized papers previously produced and are in fact favorably comparable with coated papers. They have a high gloss, high opacity, high density, good strength and are extremely smooth and bright. Their ink receptivity is good and various other characteristics render them capable of substitution for the usual coated papers. At the same time they are less brittle than coated papers due to the absence of such embrittling substances as casein. Tests conducted upon several samples of paper produced in accordance with the invention, having a calcium sulfite filler, a. rosin-wax furnish size, and a starche'glue surface size, led to the following data.

Sui-lace sized samples Basis weight-lbs Ash (as rec'd) Fol With ass saga arwas estates as 'OIM {ans e; gas s eras saga 6 BO NM a Nona.

: None.

. 1 Felt side +Purp1 Ink receptivity'.-

While the composition, character and mode of producing certain typical samples of paper. in accordance with the invention have been explained in considerable detail it will be understood that numerous variations may be made without departing fron'ithe general spirit and the invention as defined by the appended claimsA What I claim is:

1. A sm9oth,'bright book paper sheet having good ink receptivity formed from fibrous stock containing calcium sulfite as a filler to the extent of between 10 and 40% of the weight of the sheet and sizing ingredients, all thoroughly intermixed, and having a surface size consisting essentially of one or more of the class consisting of starch, glue and casein applied to at least one v face thereof, said sized surface being calendered.

2. A smooth, bright book paper sheet having good ink receptivity which consists of a fibrous base stoclg'having a body size and containing calcium sulfite as a filler to the extent of 10 to 40% of the weight of the sheet, and a surface size consisting essentially of sizing material to the extent of about one-half of one per cent of the weight of the sheet applied to at least one Div I face of the sheet, said sized surface being calendered.

3. A smooth, bright book paper sheet having good ink receptivity formed from fibrous stock containing'calcium sulfite as a filler to the extent of between 10 and 40% of the weight of the sheet and sizing ingredients, all thoroughly intermixed. and having a surface size consisting essentially of starch applied to at least one face thereof, said sized surface being calendered.

4. A smooth, bright book paper sheet having good ink receptivity formed from fibrous stock containing calcium sulflte as a filler to the extent of between 20 and 30% of the weight of the sheet and sizing ingredients, all thoroughly in-' termixed, and having a surface size consisting essentially of one or more of the class consisting of starch, glue and casein applied to at least one face thereof, said sized surface being calendered. 5. A smooth, bright book paper sheet having good ink receptivity formed from fibrous stock containing calcium sulfite as a filler to the extent of between 10 and 40% of the weight of the sheet and sizing material of the character precipitatable by acidic substances, all thoroughly intermixed, and having a surface size consisting essentially of one or more of the class consisting of starch, glue and casein applied to at least one face thereof, said sized surface being c'alendered.

- GERALD HAYWOOD. 

